1. Field of the Invention
The invention relates to a method of decomposing an organic compound, especially decomposing a cross-linked polymer, in more particular, relates to a method of decomposing an organic compound for disposal by decomposition of an organic compound such as a cross-linked polymer using alkyl carbonate.
2. Related Art
Waste disposal is a serious problem in a modern society in which there is an urgent need to deal with environmental problems. Among various wastes, polymers widely used for composite materials, etc. including various raw materials are also not an exception. In the previous examination, since fluidity of a thermoplastic polymer is increased by heating and it is thereby possible to reshape, a material recycle is proceeding. In addition, an examination of a biomass-derived polymer, which attracts attention as an alternative natural resource and due to carbon neutral properties, is actively carried on.
On the other hand, a thermosetting polymer, a cross-linked polymer and rubber are not fluidized by heating due to a three-dimensional molecule network thereof and formation is not possible, hence, the material recycle is difficult. Therefore, in many cases, those materials are sent to disposal such as a landfill, etc., even though a thermal recycle is partially carried out.
An action to try to implement material recycle for a thermosetting polymer and a cross-linked polymer is enhanced, and techniques enabling the thermal recycle are emerging. For example, JP-A 3855006 describes a method in which a cross-linked polyethylene is decomposed in supercritical carbon dioxide using nitrogen dioxide as a radical reaction initiator for obtaining a high value-added product such as adipic acid.
In addition, JP-A 2008-038006 describes a method in which C—C bond bifurcation in the cross-linked polymer is preferentially oxidatively decomposed by nitrogen oxide in the supercritical carbon dioxide for obtaining a high-molecular weight thermoplastic product. In addition, JP-A 2002-187976 describes a method in which a siloxane bond as a cross-linking bond of a silane cross-linked polymer is selectively disconnected by contact with high-temperature alcohol for thermally plasticizing.
However, in the method of decomposing a cross-linked polyethylene by the nitrogen dioxide in the supercritical carbon dioxide such as described in JP-A 3855006 and JP-A 2008-038006, toxicity of nitrogen dioxide to be used is a problematic, thus, an environmental standard therefor is set by the Air Pollution Control Act due to high adverse effect to human body (especially to a respiratory system) and strong toxicity thereof. Therefore, the nitrogen dioxide is a substance of which use should be avoided as much as possible, and development of a recycle method using a substance which is safer in use is required.
In addition, in the method using the high-temperature alcohol such as described in JP-A 2002- 87976, the siloxane bond in the cross-linked polymer is selectively disconnected and it is efficient for heat plasticization of the silane cross-linked polymer in which the siloxane bond is used for the cross-linking bond, however, it is not efficient for the cross-linked polymer not having the siloxane bond. Therefore, in the case that, for example, the cross-linked polymer not having the siloxane bond is mixed in the silane cross-linked polymer, the material recycle is assumed to be difficult.